Add 81/21 and 27/42, Solve 3 18/21 + 27/42 as a fraction

Add 81/21 and 27/42

1^st number: 3 18/21, 2^nd number: 27/42

81/21 + 27/42 is 9/2.

Find the least common denominator or LCM of the two denominators:
LCM of 21 and 42 is 42

Next, find the equivalent fraction of both fractional numbers with denominator 42
For the 1st fraction, since 21 × 2 = 42,
81/21 = 81 × 2/21 × 2 = 162/42
Likewise, for the 2nd fraction, since 42 × 1 = 42,
27/42 = 27 × 1/42 × 1 = 27/42
Add the two like fractions:
162/42 + 27/42 = 162 + 27/42 = 189/42
189/42 simplified gives 9/2
So, 81/21 + 27/42 = 9/2
In mixed form: 41/2

MathStep (Works offline)

Download our mobile app and learn to work with fractions in your own time:
Android and iPhone/ iPad